1. Field of the Invention
This invention relates to shock absorbing devices for shoes, and more particularly to liquid-filled shoe cushions. Specifically, it concerns a novel construction for, and method for producing, a partially liquid-filled cushion which is adapted to be permanently enclosed in a cavity formed in the sole of a shoe.
2. Prior Art
Pads of resilient material and liquid- and air-filled cushions, adapted to be inserted into shoes, are well known. Generally, these are intended for comfort and have limited shock absorbing ability. While they may be adequate for easing the foot strain and fatigue caused by standing or walking on hard surfaces for long periods, they offer little if any protection against repeated foot impact, such as that encountered by the active athlete in running and jumping.
Additionally, since slip-in pads and cushions tend to move about within the shoe, they are at best ineffectual, and are frequently actually hazardous to the wearer, when subjected to the severe stresses generated by the abrupt twisting, turning, starting and stopping common to most sports. The same movement tends quickly to deform and create worn spots in most such pads and cushions, thus rendering them uncomfortable and short-lived as well.
Merely increasing the thickness or stiffness of slip-in devices or of the inner soles of the shoes themselves eliminates few of these problems, and in fact creates others which make this approach to protecting the active wearer's foot from high impact forces unacceptable. In the case of the prior art attempts to provide a successful "heavy duty" shock-absorbing liquid-filled slip-in cushion, one particularly vexing difficulty which is repeatedly encountered arises from the inherent inability of the unsupported structure to withstand the enormous forces generated by the movements of athletes, such as basketball players, which cause the distended bladder literally to explode.
Various attempts have been made to construct a shoe having a sole containing a built-in pad or liquid-filled cushion. These, too, have been unsatisfactory. Padding alone does not provide adequate resilience, and efforts to construct a sole incorporating fluid-filled cavities have failed to overcome the problems of deterioration, delamination and fluid leakage.
The principal object of the subject invention is to overcome all of these deficiencies and to provide a light weight comfortable shoe which cushions the wearer's foot against the extremely high impact forces encountered in the more rigorous physical activities.
Another object is the provision of such a shoe which localizes the shock absorption at the most vulnerable areas of the wearer's foot.
Still another object is the provision of means for incorporating a shock-absorbing cushion in the shoe construction, thus preventing displacement and permanent deformation of the cushion.
Yet another object is the provision of a construction which integrates such a cushion with the shoe sole, thereby distributing the impact forces throughout the sole, rather than retaining them within the cushion.
Yet another object is the integration of such a cushion in the construction of the shoe so as to provide resistence to front, rear and side loading as well as vertical impact.
Another object is to provide a partially fluid-filled shock-absorbing cushion which may readily be mass produced.
A further object is to provide a construction of a shoe sole which permits speciality shoes to be made up with precisely the firmness and shock absorbency desired by the individual wearer.